Wavefunction tomography of topological dimer chains with long-range couplings

TL;DR

This paper demonstrates the experimental realization of photonic dimer chains with long-range couplings, enabling detailed topological analysis and phase transitions in a versatile optical fiber platform, advancing control over topological photonic systems.

Contribution

It introduces a method to implement and analyze long-range hopping in photonic dimer chains, extending the Su-Schrieffer-Heeger model with tunable phase and strength.

Findings

Successful experimental realization of long-range hopping in photonic chains

Direct measurement of band dispersion and wavefunction geometry

Observation of a topological phase transition driven by synthetic gauge fields

Abstract

The ability to tailor with a high accuracy the inter-site connectivity in a lattice is a crucial tool for realizing novel topological phases of matter. Here, we report the experimental realization of photonic dimer chains with long-range hopping terms of arbitrary strength and phase, providing a rich generalization of the celebrated Su-Schrieffer-Heeger model. Our experiment is based on a synthetic dimension scheme involving the frequency modes of an optical fiber loop platform. This setup provides direct access to both the band dispersion and the geometry of the Bloch wavefunctions throughout the entire Brillouin zone allowing us to extract the winding number for any possible configuration. Finally, we highlight a topological phase transition solely driven by a time-reversal-breaking synthetic gauge field associated with the phase of the long-range hopping, providing a route for engineering topological bands in photonic lattices belonging to the AIII symmetry class.